Down on his luck in love and life, having recently lost his job and girlfriend, 30-year-old Tom Chadwick has an unsure sense of his own identity. But when he inherits a mysterious box, Tom starts investigating his lineage and uncovers a world of unusual stories and characters, acquiring a growing sense of who he and his entire family are. FAMILY TREE kicks off its eight-episode season SUNDAY, MAY 12 (10:30-11:00 p.m. ET/PT), exclusively on HBO, followed by other episodes subsequent Sundays at the same time.

Written and created by Christopher Guest & Jim Piddock, the new comedy series is a single-camera, documentary-style show in the manner of Guest's acclaimed feature films (such as "Best in Show," "Waiting for Guffman" and "A Mighty Wind"). Chris O'Dowd ("Bridesmaids") stars as Tom Chadwick in the HBO presentation, along with Tom Bennett and Nina Conti. The series also features appearances by Carrie Aizley, Bob Balaban, Ed Begley, Jr., Maria Blasucci, Matt Griesser, Christopher Guest, Don Lake, Michael McKean, Lisa Palfrey, Jim Piddock, Kevin Pollak, Amy Seimetz, Meera Syal, Ashley Walters and Fred Willard.

Tom Chadwick (O'Dowd) has been bequeathed an old chest of curios by his great aunt Victoria. With the help of his sister, Bea (Conti), best friend Pete (Bennett) and friendly neighbor Mr. Pfister (Piddock), as well as many other well-meaning but unconventional characters, Tom embarks on his quest to learn more, following leads and clues in London that eventually bring him to the United States.

Unemployed and unattached, Tom Chadwick (Chris O'Dowd) is surprised when he's bequeathed an old chest of curios by his great-aunt Victoria, although he and his sister Bea (Nina Conti) can't remember ever meeting her. He finds an old black-and-white photo in the chest that his father, Keith (Michael McKean), believes is Tom's great-grandfather, Harry. With the help of Mr. Pfister (Jim Piddock), his avuncular neighbor, and Pete (Tom Bennett), an old school friend, Tom tracks down Neville St. Aubrey (Christopher Fairbank), a strange expert in the field of antique photos, who discovers intriguing and revealing information about Tom's ancestor. Meanwhile, Pete tries to get Tom's love life back on track by setting him up with a "model pretty" date. He's just not sure what kind of model.

When Mr. Pfister discovers an unforeseen aspect of Tom's great-grandfather Harry's life, it leads Tom and Pete to the south coast of England, where Harry died many years before. They meet Sybil (Freda Barratt), an impossibly old woman who still lives next door to the house Harry lived in and remembers him from her childhood. Their investigation takes them to a regional theatre, where he and Pete learn more than they ever wanted to know about Harry's life and loves from Rex (Hugh Sachs) and Mitch (Guy Siner), the two friendly gentlemen who run the theatre. It also inspires Tom and Pete to engage in a unique competition, but not before Pete has set Tom up on another extraordinary date.

Bea and Monk audition to perform at a children's birthday, while Tom starts digging deeper into the life of his grandfather William, who he suspects might have competed in the 1948 London "Austerity Games," a far cry from those of 2012. After learning more about the games from Mr. Pfister, Tom visits his great-aunt Victoria's friend Mildred (Barbara Bolton), who is able to shed some light on William's former athletic prowess, and on why Victoria left Tom the chest of family curios. With Keith's help, Tom and Pete visit the gym where Tom's grandfather William trained for the Games, and meet some old-timers who actually knew him. While at the gym, Pete bravely accepts a challenge from a much younger timer. Bea and Monk perform their first professional gig at a wedding reception.

Tom finally has an interview for a job. He also discovers he has cousins in both Derbyshire and California, and makes a plan to visit and learn more about the Derbyshire branch of the family tree. Meanwhile, Pete has to perform a delicate "procedure" on an alpaca at the zoo. Tom, Bea, Keith, Luba (Lisa Palfrey) and Monk drive up to the Derbyshire farm owned by their cousins from the North. Tom is interested to find out if the grass is really greener in the country, and equally determined to get to the bottom of a dark family secret. Culture clashes notwithstanding, Tom gets his answers and some family truths are finally revealed. The family-tree plot thickens as he also hears from his American cousin, Al (Ed Begley, Jr.), on the trip. Pete's life-affirming mission at the zoo proves to be a no less sticky venture.

For more on the series, visit Facebook.com/HBO and twitter.com @HBO #FamilyTree.

FAMILY TREE is a Lucky Giant/HBO co-production in association with NBCUniversal and the BBC; written and created by Christopher Guest & Jim Piddock; executive produced by Christopher Guest, Jim Piddock, Karen Murphy, Deborah Oppenheimer and Mario Stylianides; directed by Christopher Guest.